The present invention relates to a clockwork movement fitted with a generator, in particular for a wristwatch.
The use of batteries or accumulators is a factor limiting the features of the apparatus, for all applications, and in particular for a watch. Indeed, changing or recharging the batteries or accumulators affects the availability and reliability of the watch.
In this context, the conventional mechanical watch has a certain advantage in watchmaking know-how: such a watch is permanently available. The recharge of powerxe2x80x94which is purely mechanicalxe2x80x94is achieved simply by rewinding the watch mechanism.
This type of watch uses a manual or automatic winding device generally coupled to a regulating device commonly called a xe2x80x9cSwiss lever escapementxe2x80x9d. It is difficult to obtain a high level of precision with this regulating device. This system is also relatively expensive.
The other large family concerns the conventional quartz watch. A battery simultaneously powers an electric motor and a device for regulating the working of the motor. The motor rotation is controlled by a nominal frequency supplied by a quartz. This provides a high level of precision for the time indication. However, this device is relatively noisy since the forward movement of the second wheel is saccadic and the battery has to be changed periodically.
New types of watch have been made combining the two aforecited systems and exploiting their respective advantages. In these constructions, mechanical power storage has been associated with quartz regulation, supplied with electric power by a generator driven by a mechanical part coupled with a power storage spring.
The article by MM Born, Dinger and Farine xe2x80x9cSaltoxe2x80x94An automatically wound mechanical movement with the precision of a quartz movementxe2x80x9d which appeared in the Swiss Chronometry Society publication xe2x80x9cSSC study days 1997xe2x80x9d, pages 55 to 63 may also be cited as the corresponding state of the art.
The arrangement of the generator according to this prior art is illustrated in FIG. 1 annexed hereto, showing a top view of a partially assembled clockwork movement, and in FIG. 2 annexed hereto, which is a cross-section of FIG. 1. This generator includes a rotor with two flanges 8 arranged on either side of three flat coils 11 forming the stator and offset by 120xc2x0 with respect to each other relative to the rotor axis, in a same orthogonal plane thereto.
Six magnets 9 are fixed radially and at regular intervals on each flange 8, facing coils 11. Two consecutive or facing magnets 9 have opposite polarity. A printed circuit 6 is secured to plate 4 and is used as a support for coils 11.
Electric circuit 10, which has a low power consumption, is powered by an electric generatorxe2x80x94formed by the shaft assembly of rotor 5, flanges 8, magnets 9 and coils 11xe2x80x94driven via the kinematic connection 3 by barrel device 2. The mechanical power stored in barrel 2 thus drives the rotor. The passage of magnets 9 in proximity to coils 11 generates a substantially sinusoidal induced voltage across the terminals of coils 11.
FIG. 3 annexed hereto demonstrates schematically the fact that the assembly of the monoblock rotorxe2x80x94formed of parts 5, 8 and 9 in the completed device is currently achieved by inserting shaft 5 laterally between two fixed coils 11. The monoblock rotor cannot be inserted vertically since the three coils 11 are fixed and flanges 8 located on either side of these coils must partially cover them. As is clear in particular from FIGS. 2 and 3 of the aforecited document, coils 11 have a space, referenced Dmin in FIG. 3 annexed hereto, at least as wide as rotor shaft 5, having a diameter D at its centre, to allow the shaft to be inserted laterally until it is placed definitively at the centre of the three coils. Because of the space thereby arranged between the three coils 11 offset angularly by 120xc2x0, a mediocre covering of coils 11 is obtained by magnets 9, which causes a drop in the yield of the micro-generator, and a relatively large space requirement. In other words, the number of turns of coils 11 superposed onto flanges 8 carrying magnets 9 at their periphery is limited.
The object of the invention is to overcome these drawbacks. The invention therefore concerns a generator of the clockwork type including on the one hand a rotor including two flanges carried by a shaft, this shaft and the flanges being fixed in rotation when operating, magnets, even in numbers, being fixed to each flangexe2x80x94two consecutive or facing magnets having opposite polarityxe2x80x94and including on the other hand a stator formed of at least three coils with axes parallel to that of the rotor, and arranged on a support, these coils being arranged between the two flanges fitted with magnets after the generator is assembled and arranging between them a sufficient central space for said rotor shaft. This generator is characterised in that the rotor is formed of at least two distinct parts prior to its assembly to said stator which each include one of the two flanges so that the generator is assembled by introducing the rotor shaft in said central space arranged between the coils in a direction perpendicular to the general plane defined by the coils, the distance separating any two adjacent coils being less than diameter D of said shaft at its centre.
The space separating two adjacent coils can thus be reduced and even removed for certain dimension of the coils.